feat: add Claude Fable 5.1

package.json

@@ -32,7 +32,7 @@
   },
   "dependencies": {
     "@anthropic-ai/claude-agent-sdk": "^0.2.117",
-    "@anthropic-ai/claude-code": "^2.1.198",
+    "@anthropic-ai/claude-code": "^2.1.257",
     "cross-spawn": "7.0.6",
     "jsonc-parser": "^3.3.1",
     "libsql": "^0.5.29",

src/__tests__/explicit-model-pins.test.ts

@@ -13,7 +13,7 @@ import { describe, it, expect, mock, beforeEach } from "bun:test"
 
 // ---------- unit: explicitModelPin + canonical bump ----------
 
-const { explicitModelPin, CANONICAL_SONNET_MODEL, CANONICAL_OPUS_MODEL } = await import("../proxy/models")
+const { explicitModelPin, CANONICAL_FABLE_MODEL, CANONICAL_SONNET_MODEL, CANONICAL_OPUS_MODEL } = await import("../proxy/models")
 
 describe("explicitModelPin (#631)", () => {
   it("pins fully-versioned sonnet ids", () => {
@@ -29,6 +29,7 @@ describe("explicitModelPin (#631)", () => {
 
   it("routes mythos ids through the fable tier pin", () => {
     expect(explicitModelPin("claude-mythos-5")).toEqual({ ANTHROPIC_DEFAULT_FABLE_MODEL: "claude-mythos-5" })
+    expect(explicitModelPin("claude-fable-5-1")).toEqual({ ANTHROPIC_DEFAULT_FABLE_MODEL: "claude-fable-5-1" })
     expect(explicitModelPin("claude-fable-5")).toEqual({ ANTHROPIC_DEFAULT_FABLE_MODEL: "claude-fable-5" })
   })
 
@@ -58,6 +59,12 @@ describe("canonical opus pin", () => {
   })
 })
 
+describe("canonical fable pin", () => {
+  it("bare fable means the current Fable", () => {
+    expect(CANONICAL_FABLE_MODEL).toBe("claude-fable-5-1")
+  })
+})
+
 // ---------- integration: pins reach the SDK subprocess env ----------
 
 let queryEnvs: Array<Record<string, string | undefined>> = []

src/__tests__/openai.test.ts

@@ -1320,26 +1320,29 @@ describe("createSseTranslator", () => {
 // ---------------------------------------------------------------------------
 
 describe("buildModelList", () => {
-  it("returns 8 models", () => {
-    expect(buildModelList(true).length).toBe(8)
-    expect(buildModelList(false).length).toBe(8)
+  it("returns 9 models", () => {
+    expect(buildModelList(true).length).toBe(9)
+    expect(buildModelList(false).length).toBe(9)
   })
 
-  it("includes sonnet-5, fable-5, opus-5, opus-4-6, opus-4-7, and opus-4-8 for UI pickers", () => {
+  it("includes current and legacy Fable plus the supported Sonnet and Opus models for UI pickers", () => {
     const ids = buildModelList(true).map(m => m.id)
     expect(ids).toContain("claude-sonnet-5")
+    expect(ids).toContain("claude-fable-5-1")
     expect(ids).toContain("claude-fable-5")
     expect(ids).toContain("claude-opus-5")
     expect(ids).toContain("claude-opus-4-6")
     expect(ids).toContain("claude-opus-4-7")
     expect(ids).toContain("claude-opus-4-8")
   })
 
-  it("Max subscription gets 1M context for fable, 200k otherwise", () => {
-    const fableMax = buildModelList(true).find(m => m.id === "claude-fable-5")!
-    const fableFree = buildModelList(false).find(m => m.id === "claude-fable-5")!
-    expect(fableMax.context_window).toBe(1_000_000)
-    expect(fableFree.context_window).toBe(200_000)
+  it("Max subscription gets 1M context for every Fable version, 200k otherwise", () => {
+    for (const id of ["claude-fable-5-1", "claude-fable-5"]) {
+      const fableMax = buildModelList(true).find(m => m.id === id)!
+      const fableFree = buildModelList(false).find(m => m.id === id)!
+      expect(fableMax.context_window).toBe(1_000_000)
+      expect(fableFree.context_window).toBe(200_000)
+    }
   })
 
   it("Max subscription gets 1M context for all opus variants, 200k for sonnet", () => {

src/__tests__/pricing-unit.test.ts

@@ -45,6 +45,7 @@ describe("resolveModelPricing", () => {
   it("resolves concrete API model IDs", () => {
     expect(resolveModelPricing("claude-opus-4-8")).toMatchObject({ inputPerMTok: 5, outputPerMTok: 25 })
     expect(resolveModelPricing("claude-sonnet-4-6")).toMatchObject({ inputPerMTok: 3 })
+    expect(resolveModelPricing("claude-fable-5-1")).toMatchObject({ inputPerMTok: 10 })
     expect(resolveModelPricing("claude-fable-5")).toMatchObject({ inputPerMTok: 10 })
   })
 

src/__tests__/proxy-env-stripping.test.ts

@@ -220,7 +220,7 @@ describe("SDK model pin injection (fixes #419)", () => {
     const app = createTestApp()
     // Bare alias: no envOverride kicks in, so the canonical pin is exercised.
     await post(app, { ...BASIC_REQUEST, model: "sonnet" })
-    expect(capturedQueryOptions.env.ANTHROPIC_DEFAULT_FABLE_MODEL).toBe("claude-fable-5")
+    expect(capturedQueryOptions.env.ANTHROPIC_DEFAULT_FABLE_MODEL).toBe("claude-fable-5-1")
     expect(capturedQueryOptions.env.ANTHROPIC_DEFAULT_OPUS_MODEL).toBe("claude-opus-5")
     expect(capturedQueryOptions.env.ANTHROPIC_DEFAULT_SONNET_MODEL).toBe("claude-sonnet-5")
     expect(capturedQueryOptions.env.ANTHROPIC_DEFAULT_HAIKU_MODEL).toBe("claude-haiku-4-5")
@@ -238,9 +238,15 @@ describe("SDK model pin injection (fixes #419)", () => {
     expect(capturedQueryOptions.env.ANTHROPIC_DEFAULT_FABLE_MODEL).toBe("claude-fable-5")
   })
 
+  it("explicit claude-fable-5-1 requests pin the SDK env to Fable 5.1", async () => {
+    const app = createTestApp()
+    await post(app, { ...BASIC_REQUEST, model: "claude-fable-5-1" })
+    expect(capturedQueryOptions.env.ANTHROPIC_DEFAULT_FABLE_MODEL).toBe("claude-fable-5-1")
+  })
+
   // Mythos has no SDK alias of its own — it resolves through the fable alias,
   // so an explicit claude-mythos-* request must pin ANTHROPIC_DEFAULT_FABLE_MODEL
-  // to the requested id (not Meridian's canonical claude-fable-5 pin).
+  // to the requested id (not Meridian's canonical claude-fable-5-1 pin).
   it("explicit claude-mythos-5 requests pin the SDK env to mythos via the fable alias", async () => {
     const app = createTestApp()
     await post(app, { ...BASIC_REQUEST, model: "claude-mythos-5" })

src/__tests__/proxy-health-build.test.ts

@@ -94,6 +94,7 @@ describe("/v1/models profile auth context", () => {
       envOverrides: { CLAUDE_CONFIG_DIR: "/profiles/work" },
     }])
     expect(models.get("claude-opus-4-6")?.context_window).toBe(1_000_000)
+    expect(models.get("claude-fable-5-1")?.context_window).toBe(1_000_000)
     expect(models.get("claude-fable-5")?.context_window).toBe(1_000_000)
   })
 

src/proxy/models.ts

@@ -40,7 +40,7 @@ export type ClaudeModel = "sonnet" | "sonnet[1m]" | "opus" | "opus[1m]" | "haiku
  * override via MERIDIAN_DEFAULT_{TYPE}_MODEL (proxy-side) or
  * ANTHROPIC_DEFAULT_{TYPE}_MODEL (shell env, wins over Meridian's pin).
  */
-export const CANONICAL_FABLE_MODEL = "claude-fable-5"
+export const CANONICAL_FABLE_MODEL = "claude-fable-5-1"
 export const CANONICAL_OPUS_MODEL = "claude-opus-5"
 export const CANONICAL_SONNET_MODEL = "claude-sonnet-5"
 export const CANONICAL_HAIKU_MODEL = "claude-haiku-4-5"

src/proxy/openai.ts

@@ -1064,6 +1064,15 @@ export function buildModelList(extendedContextIncluded: boolean, now = Math.floo
       context_window: extendedContextIncluded ? 1_000_000 : 200_000,
       capabilities: FULL_CAPABILITIES,
     },
+    {
+      id: "claude-fable-5-1",
+      object: "model",
+      created: now,
+      owned_by: "anthropic",
+      display_name: "Claude Fable 5.1",
+      context_window: extendedContextIncluded ? 1_000_000 : 200_000,
+      capabilities: FULL_CAPABILITIES,
+    },
     {
       id: "claude-fable-5",
       object: "model",